The reasons for unsuccessful attempts to establish pregnancy can be attributed equally to male and female fertility disorders. Today many different assisted reproduction techniques are available. These techniques are used to induce multiple and synchronous follicular growth and thereby obtain fertilizable oocytes.
The current standard treatment is to induce multiple follicular development by administering high doses of HMG (Human Menopausal Gonadotropin). This results in ovarian hyperstimulation. Upon reaching a suitable degree of oocyte maturation using these techniques, ovulation is induced by the administration of HCG (Human Chorionic-Gonadotropin) in order to obtain a sufficient number of oocytes. During this time, the clinic-infrastructure preparation can begin. Preparation includes recovery of oocytes by abdominal or transvaginal puncture, intracorporal or extracorporal fertilization of oocytes by different techniques and embryo replacement into the uterus. Routinely, beginning pregnancy is supported by additional administrations of HCG or progesterone. Today this treatment is applied to clinical conditions of male and female infertility.
Complications that are frequently observed during the hyperstimulation procedure are:
A: premature surges of luteinizing hormone (LH) at a premature maturation state with a rupture of the follicles that induced a subsequent cancellation of the treatment occurring in about 25% of the patients; and B: ovarian hyperstimulation syndromes induced by exogenous gonadotropins which in severe cases require hospitalization and are life-threatening.
In order to avoid premature LH-surges, today LHRH-agonists are used as a comedication. By continued administration of these drugs, a complete suppression of endogenous gonadotropins is achieved by desensitization of pituitary cells and down-regulation of their receptors. Subsequently, the gonadotropin levels can be controlled by exogenous injection and the pituitary is refractory to the stimulation of LH-release by increasing levels of estradiol. Disadvantages are 1) a long treatment period until the suppression and down-regulation occur; 2) estrogen withdrawal symptoms; 3) disturbance of the normal menstrual cycle; 4) the need for frequent hormone determinations in order to evaluate the time of onset of suppression; and 5) high dose HMG treatment is needed for ovarian stimulation.
The pathogenesis of hyperstimulation syndrome is not completely understood, but is thought to be associated with the use of HCG for ovulation induction and luteal phase support.
One recent approach involves the use of the LHRH antagonist Cetrorelix (INN). In first clinical trials, short term treatment with Cetrorelix resulted in a complete avoidance of premature LH surges during stimulated cycles and the need for HMG. Due to the immediate suppression of gonadotropins by this antagonist, the unwanted stimulatory phase and also the withdrawal of estrogen produced by the agonists was avoided. The duration of treatment was also significantly shortened. In addition, it was shown that a single injection of an antagonist, given in the mid-follicular phase, would adequately suppress premature LH surges.